Time multiplex television in color



J. A. BURTON TIME MULTIPLEX TELEVISION IN COLOR Dec. 25, 1951 4 Sheets-Sheet l Filed May l, 1948 LUM/L15l CE NT PHOSPHORS EM TL AH R 0L mr. EN

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LAYER J GREEN LAYER 24 LOW VOLTAGE LIGHT t EMISSION DIS TNCE en mim no ESG una s m2 amm n man pms l Euwe r m IEE. H w AW m L w.. R E DE M656 ww., NMNs TT YmAEE u L wauw o mum amwam EP N/T Y. TM. ou 7 rc Suns... 6 wA 4 mmf nurnu 4 mvn oxnnu 0 E 1Mo W0 MCF-f A w n mw l| L Nac M am l sc 5 f 4 m 4 r ma u flu an F so R w u.. U A f N N 4 2 m 4 Aw /NVEAl/TOR AJ. A. BURTON ATTORNEY Dec. 25, 195] J. A. BURTON TIME MULTIPLEX TELEVISION Filed May l, 1948 COLOR 8 VERT/CAL SYNCH. PULSE IN COLOR 4 Sheets-Sheet 5 A TTORNE V 4 sheets-sheet 4f n-c ONE' COMPLETE FRAM 8555 ONE FIELD J. A. BURTON TIME'MULTIPLEX TELEVISION 1N COLOR Il s l1 m R G o. mv u N R 5 6 e 3 n a m n M M a w l l E o D M E .n n N rival' n 5 l E .wf J w u 6 l llllllllllnJ/ll I I 0 N m 5 6 a n M a f V R 6 6 [-2.14 G 5 w o D 3 ...n A! ,l n 7 .J l l/ M m m w I Dec. 25, A1951 Filed May l, 1948 Patentecl Dec. 25, 1951 UITED i CE' 7 Claims... (Cl. 17E-#1) This invention relates to electro-optical color systems. w

An object of the invention is to provide anc improved device for producing different colors on a viewing screen.

Another object is to provide an improved tele vision system for producingimagesin color.

A feature of this' invention is a cathode ray` tube having a multilayer luminescent screen, each layer consisting of a material which luminesces` with a characteristic color when bombarded'fwith' electrons at a suitable velocity. If the tube is tov be used for color television the screen might con sist of three superimposed layers adapted to emit red, green and blue light, respectively; The color emitted is determined by the velocity ofvthe electrons when they strike the screen.

Another feature of the invention is a television system comprising such a cathode ray tube with; a multilayer luminescent screen and meansto acL celerate the electrons of the scanningY cathode rayl beam to 'produce the necessary color components to produce an image in natural color. For example, the material of the layer nearest the electron gun might be a phosphor giving red light*` emission, the intermediate layer a phosphor giving* green light emission, and the layer farthest from` the electron gun a phosphorA giving blue light* emission. Because of the fact that the energy lossY per unit distance is much greater for slow elec--v trons than for fast electrons, most of the light emission will be produced in the regions of the phosphor Where the electrons are stopped and relatively less light is produced in the regions of' the phosphor that are traversed' when the electrons still have a high velocity. For a low velocity electron beam the electrons are substantially all stopped in the red light emitting layer so that only red light is produced. With a medium voltage beam the electrons pass through the phosphor giving red light emission at high velocity producing relatively little red light While-most of the energy loss occurs near the end of the elec-V tron path in the phosphor giving green light so that the green light emission is much more intense thanvthe red light emission. With a still higher voltage beam the electrons pass through the layers of phosphors giving red and green light emission at high velocity and end their pathsinthe layer of the phosphor giving blue light emis sion resulting in the emission of preponderantly blue light With relatively little red and green light. The voltage for aceelerating'the electron beam and so determining the velocity of the electrons may befcontrolled'lay-suitable signals sentbythe detail having: reference. to the accompanying' drawings.

Fig. 1 illustrates. diagrammaticallyone' illus. trative embodiment of the invention;v

Fig. 2-is1a detail ofLa portion of the cathode ray tube ofAV Fig. lY showingin cross-section the multilayer. luminescent iscreen;

Fig. 3 showsY idealized;- qualitativev y graphsilluse trative'oftheoperation of the invention;

Fig.- 4- is a; schematic diagram of: a televisione receiving `system according to* the-invention.;

Figs. 5 t'o 91- illustrate circuit details of the sys-V tem offFig; 4S; and

Fig. 10 'shows graphs illustrative of the opera-fv tion ofthesystem-illustrated in Figs. 4 130,9.

Like-elements in the several gures of thev` draw.- ing: areA identified by the sameV reference char' acter.

Referring novvv to Fig; l; .anevacuated cathode ray tube# lfll'i's. providedi Witha three-layer luminescent screen l'lf oni the enlarged viewing; end` wall 9i This` catho'd'eray tubev l0 is also pro.- videdwith an:-indirectly heated.v electron emitting cathodel- IT; a control electrode or grid [3'.y rst and' second` anodes lli and' i5, respectively,` vertical deectin'g plates' lli.: and il, horizontal;

2U'consistingof a conductive coating 2|; on the inside of the ared Walls of the tubey l 0f and al line Wire mesh 22; in contact With the coating 2l andpositioned'parallel tor-but .separated from the luminescentscreen ll.

'Iherconstruction of thevlumines'cent screen H1 is' illustrated in Fig. 2 which is a cross-section of a detail of the enlarged? viewing endl Wall 9" oftube lil, luminescent screen ll andi WireV mesh 22a The luminescent screen ll consists of three layers of phosphors, each layer producing light of a different color when bombarded by electrons. having' suitable velocity. Layer 23f carriedv byV the end' Wall 9 may consistI of zinc sulphide activatedwith silver, ZnS'zAg, which is a. blueuo-f rescingY material. Layer 2lwhichoverlies'and issupported by layerA 23 may consist off'zinc sulphide activatedrwith copper, ZnS: Cu, which is a green nuorescing material. Layer 25. which overlies and'v is supported by layer 24 may consist of zinc cadmium sulphide, Zn,CdS, which is: prepared in such away-as to producev a red 11110- rescing material. A thin metallic layer 26 which can be easily penetrated by electrons overlies and is supported by layer 25. Aluminum might be used for the metallic layer 26 and applied by evaporation. The thickness of the layers in Figs. 1 and 2 is greatly exaggerated for clearness of illustration. The invention is not limited to the use of these specific luminescent materials.

It is well known that the energy lost per unit distance traveled by an electron beam in a solid increases as the electrons lose energy and is approximately inversely proportional to the energy of the electrons. With this in mind, it occurred to applicant that it might be possible to make a laminated phosphor screen which would have three phosphor layers, for example, one for red emission, one for green emission and one for blue emission. The energy of the bombarding electrons could then be controlled so that the greatest loss of energy would occur in the phosphor layer which would give the desired color. Thus the voltage of the electron beam would control the color of the light emission and the beam current would control the brightness.

This concept was embodied in the cathode ray tube l described hereinbefore in connection with Figs. 1 and 2. Electrons from the cathode I2 controlled as to number by the control electrode i3 are formed into a beam by anodes I4 and Yl5 and deiiected as desired by deflecting plates I6 and il, and I8 and IS. The wire mesh electrode 22 at the same voltage as the second anode i prevents disturbances of the focussing and deflecting operations. The voltage for controlling the penetration of electrons of the electron beam into the luminescent screen Il is impressed between the metallic layer 26 and the mesh electrode 22. To produce red light this voltage is of a value such that the electrons of the beam are stopped in the red iiuorescing material of layer 25. To produce green light the voltage is of a value such that the electrons of the beam pass through the red light producing layer 25 at high velocity and therefore without much loss of energy and are stopped in the green fluorescing material of layer 24 resulting in a much greater emission of green light than of red. To produce blue light the voltage is still higher and of such a value that the electrons of the beam pass through both the red light producing layer 25 and the green light producing layer 24 at high velocity without much loss of energy and are stopped in the blue fluorescing material of layer 23 resulting in a much greater emission of blue light than of red and green light.

The foregoing effect is shown qualitatively and in idealized form by the graphs of Fig. 3. The abscissas represent penetration of the electrons from the cathode ray beam into the layers of the luminescent screen Il and the ordinates represent light emission from the layers. Graph 21 shows the emission of red light by the electrons which are stopped in the layer 25, the area under the graph representing the total light emitted. Graph 28 shows the emission of green and red light by electrons which pass through the layer 25 and are stopped in the layer 24. The emission of green light is predominant. Graph 29 shows the emission of blue, green and red light by electrons which pass through layers 25 and 24 and are stopped in layer 23. The emission of blue light is predominant. It is thus seen that by controlling the voltage impressed on metallic electrode 26 and wire mesh 22, the color of the light emitted by luminescentl Screen ll may be made predominantly red, green or blue, as desired.

The cathode ray tube just described may be embodied in a color television system according to another feature of this invention. Such a system is shown schematically in Fig. 4. This system involves at the transmitter only a relatively small change from accepted present practice. A television camera tube, such as an iconoscope, image dissector, or image orthicon tube is used with red, green and blue optical lters which are moved mechanically in front of the objective lens of the system. These filters are moved in synchronism with the field scanning so that successive iield scannings correspond to the desired red, green and blue color mixing components, respectively. The optical absorption characteristics of these lters is matched with the spectral response of the photoelectric pick-up device and with the spectralV distribution of the light emission of the three phosphor layers 23, 24 and 25 of the cathode ray tube i0 in such a way that the camera tube and red lters will have approximately the same spectral response as the red emission from the phosphor layer 25 when the accelerating voltage of the cathode ray beam is such as to excite the red phosphor most eiiiciently. Similarly, the blue and green lters with the camera tube are chosen to match the emission from the blue and green phosphor layers, respectively, when the accelerating voltages of the cathode ray beam are such as to excite them predominantly. Thus, in operation, the camera tube with the system of mechanically rotated optical filters is sensitive rst to red light, then to green light and then to blue light cyclically, the change from one color to the next being made between successive field scannings.

The resulting video signals with the necessary synchronizing signals are transmitted over any suitable television channel, one such channel being a radio channel, for example. The only essential new component of such signal is a synchronizing pulse for maintaining the color of the light emission at the receiver in synchronism with the color sensitivity of the camera tube. In a well-known system for black and white television the video signal is transmitted line by line with a line scanning synchronizing pulse transmitted between each line scanning. At the end of each field scanning there is also transmitted a vertical Scanning synchronizing pulse with suitable equalizing pulses. For color according to an illustrative embodiment of this invention every third eld scanning synchronizing pulse is characteristie of a color cycle. This system is adaptable to interlaced scanning which is now generally adopted for black and white television. With interlaced scanning according to the R. M. A. (Radio Manufacturers Association) standards there are sixty field scannings per second, each two adjacent eld scannings being interlaced t0 form one frame scanning at the rate of thirty frame scannings per second. According to the color system of the present invention the color changes at the end of each eld scanning and a color cycle requires one-twentieth of a second so that color cycles occur at the rate of 20 color cycles per second. This relationship is shown in Fig. l0 (A) where time is represented horizontally from left to right in the direction of the arrow. v

The corresponding synchronizing pulses according to an illustrative embodiment of this invention `are shown in Fig. 10 (B). The line scanning synchronizing pulses35 are represented schematlcallyfy by vertical. linesr: sincea iir actual. system?. there: are many:` more pulsesf per eld scanning f than. can` be; shown.. on .thea time'. scale. ofrFig; Furthermore;.inithisillustrative eme bodimenttherare;v air oddnumberrof :linescanning pulses perlcompletef. frame to =e1ect inter:- lacing; The.v oraslinary:v field; scanning synchronizingpulses; areiof.`x considerably. longer dura.-

tion. than theline scanning synchronizingspulses..

The2 equalizing: pulses; mentioned;` hereinbefore.'`

are. not;sho.wn; Thei color cycle synchronizing` pulses; 31.2 occur.' ati. the: end of". everythirdiield scanning and: are: characterized. by a; duration` considerably longer: than; that lofi the;A el'dz syn'- chronizing pulses. 3.6i.- The.- color' cycle. synchro;- nizing pulses ,321? are also: accompaniedby' equal'- izing pulses.l (not shown)v since'. these. pulseszalso. function.A as field scanning synchronizing; pulses..

The synchronizing` pulse. signals therefore con;` sist. of short: duration horizontall lineV scanning.

synchronizing pulses; 3 5.; medium duration vertical eld scanning: synchronizing pulses'. 36,. and long duration color cycle and eld. scanning. synchronizing pulses.` 31.. These; synchronizingv pulse. signals.wouldlbegeneratedat thetransmit ter.: by means of.' welll-known:` types of"multivi brator: circuits.

Atgthereceiven illustratedainz Fig. .4 ithe transmitted video and synchronizing. pulse signals would be utilized after: detection-off. the radio. signal tofv produce. an observable. image oir. the three-layer:luminescentscreen. |1| of cathode ray tubeA |01. The .transmittedradio signal ispicked up by an antenna. 40. and-lathevideo andn synchronizing pulse signals. obtained vby double dey tectionzinza first/.detector 4|: locally energized by current; from.. intermediatev frequency oscillator. 12,V amplified by intermediate frequency Vamphi-ler l|3-` and nally detected byJA secondl-y detector` 44.

The synchronizingscanning.V and.. color' cycle.

pulses are .separatedfrom theavideosignals by the synchronizing selector.; circuit `45. The. video signals are. amplified in .video amplier146. and impressedlon .the control electrodeiofA cathode ray tube |10 to control: theintensityL-of or.: number. of.' electrons in... the` cathodeI :ray: beam which` bom.-

ning and. color cyclepulses are.`Vl impr-essedi` on the horizontal and verticali deflection circuiti` 4.1.:

and thecolor-cycle synchronizingwcircuit 48. The elements or the horizontal l'andtverticaldeflection circuit. are' effectively'identical' withY circuits now -in use-*for blackandwhite television with` interlaced scanning. The horizontal deection.:

iscontrolled by the line scanning. pulses35'1fand the accompanyingequalizing pulses. The vertl calvdeflectionr is controlled bythe ordinary el'd scanning synchronizingpulses 36 and/falso by the colorf cycle-synchronizing pulses 311 off longer duration. Thus thevertica'l.. iield. scanningsare started each one-sixtieth of a. second. by either of these. twostypes ofi pulses:

The. color; cycle. synchronizing.: circuiti 48 functions to` producer an. accelerating voltage. which isimpressedbetween the-iwire mesh 22 and the thin metallici layer- 26. of.. cathode-.ray tube I0.. Conductor 5.0 is...connected. to layer 26"and. conductor 49; to;k Wire mesh122, the arrangement of circuit 48 being such that .conductor 50.is Ypositivewith respect to: conductor'49i. TheI voltage' impressed on conductor50 is represented.` bygraph-f 5| Fig. 4i.. Y

The connectingV circuit between-'- the synchro'- nizingselector---circuitll and? the:A colorA cycle` synchronizing` circuit? 481" represented by the line-:52... This circuit; may beza Apair onconductorss (B). carried by circuit.52 are impressed on. the..

duration Selectioncircuitf. 53. The' eldl scan.w

ningsynchronizing pulses 36. and the color.: cyclei synchronizingpulses] only are-shown graph. 58; Fromthe pulses.' of graph 58 the selection? circuit 56` selectsonly thel colorv cyclesynchronizing pulses: 88fshown .by graph. 5.9:. The pulses;

88; are impressed. simultaneously on. multivibrators154.and. 55; Multivibrator 54.' is;so. constructed thatafter. being. triggered by a pulse" 88i it-. re.-

mainsiactive for. the periodof two eld scanningsf.

and' inactive. for one hield scanning: as: shown.. by-graphi. Multivibrator 55 is triggeredat.. the

same time by pulse y8.8 butgitremainsv active for.;Y

the duration of one eld scanning. and inactive.. for two field scanningsas shown by graph 6|. The relation of these graphs. 60 and..6;| to: the elcl scannings isl shov/nby. the. similarly num;- bered. graphs in Fig.. 10- (C) and. (D)

The output voltages: of-'S multivibrators, 54s and 55 control respectively the. conductivity 'on triodes 56 and 51. The high voltagepower supply +V iscoinmonto both .highvoltage triod'es:'56iandl5t'li. The anodeof.v triode..56..is. connected to. thepcwer supplyv -I-Vthroughresistors 62.and 63.in series while the anode: of' triode 51; is: connected. to` the;

power: supply` +V. only through resistor'.y 63.v

Triodes- 56-.and--5-1. are biased respectively bybias.- ing sources. representedby: batteries. 64tand165. so that. when theiri grids are. at'. zerorpotential.' that' is;` ground.v potential. no` current?.` passes: in. them: and theroutput. voltage; will then. berth'e;

resistor 63?due to current flowing'inthei'cathode: ray tube. The resistancev ofzresistori63 Wouldrba made suiciently small so astokeep such-:voltage drop small. Whenthe'No'. 1: vibrator Emis-.active and therefore itsoutputvoltageis positive making; thelfgridi of. triode.. 56 positiva. triode; 56 passes:

current' .and thevolta'gezof. conductor5ifallsto a'.-

value: lower` than; that of: source +V. For ex.-A ample, if. the. resistance values-I of resistors 62.

and .63.fare equal andzif the. voltagedrop in the.

triode' 56? is. muchr lessA than.. the". voltage of; theV source +VWhen1the gridy of triode 56is.positiv.e, then .thelvolt'age ofthe output conductor.:50. will be verynearly one-half thatof the'. source |-V.`

When the. No. 2."..multivibrator` 55. isl active'. and r therefore its outputv voltageisypositive.making-the' grid offtriode I51 positive, triode 51 passes current" so -thatth'e voltage thereacrossz is very low, say' onlya few'hundred volts comparedwith the voltagev of the sourcel -l-V which might be200002 volts'.` The voltage of conductor 56- therefore isf +20,-00'0i volts` when nei-ther of' multivibrators` 54' and 55 isf active; |10,000 volts when multivibrator 51%l valone is'active and approximately-zero'voltsewhen multivibrator 55 is Iactive;

vThese' voltage conditions iii-relationship to4 ther i fiel'dlscannings is.shown .by-fgraph; 5| inl Figi.. 10i' (E) l Where' `Vf` representsfthe fvoltage' of the high i voltage; power?. source; +V.. Underfthesex. condi@ andere.:

tions it is seen that the electrons of the cathode ray beam in cathode ray tube l are accelerated very little in their travel from Wire mesh 22 to metallic layer 28 during each red eld scanning but are accelerated by a voltage 1/2 Vo during each green eld scanning and by voltage Vo during each blue field scanning. These voltages added to the normal accelerating voltage of the cathode ray tube cause a penetration of the three-layer luminescent screen Il of cathode ray tube l0 to produce light emission of the necessary colors to produce television images in color. f

An example of a, duration selection circuit 53 is shown in Fig. 6. The long duration color cycle pulses 31 are distinguished from the shorter duration eld scanning pulses 36 by an integrating circuit 66 comprising a resistor 61 and a condenser 88. The voltage across condenser 68 is impressed on the grid of triode 69. The cathode of triode 69 is normally biased well beyond cutoff by a source of biasing voltage represented by battery 18. The integrated voltage as it appears across condenser 68 is represented by graph 1| of Fig. (G) The shorter duration eld scanning synchronizing pulses 38 when integrated appear as pulses 38 in graph 1I of less amplitude than the integrated color cycle pulses 31. Because of the negative bias on triode 69 from battery 18 represented by the distance C in Fig. lO (G) the smaller amplitude pulses 36 do not appear in the output circuit of triode 69 and only pulses corresponding to the larger amplitude color cycle pulses 31 appear as shown in Fig. 10 (F).

In the circuit of Fig. 6 a start-stop multivibrator is shown connected to the pulse inverter triode 69 by conductor 16 and also to conductor 52 by conductor 14 through pulse inverter 12 by conductor 11. This type of multivibrator is positive in action and readily controlled by the synchronizing pulses in the embodiment of applicants invention selected for illustrative purposes. Conductor 16 is connected to the starting element and conductor 14 to the stopping element of multivibrator 15. Multivibrator 15 as illustrated in Fig. 6' is so adjusted as to produce an output voltage the same as the output voltage of .No. l multivibrator 58 of Fig. 5. This voltage is represented by graph 69.

Details of the circuit of multivibrator 15 are shown in Fig. 7. This multivibrator comprises two triodes 18 and 19, anode resistors 80 and 8I,.

switching condensers 82 and 83, grid biasing resistors 8d and 85, cathode resistor 86 and grid resistor 81. The adjustment' of this circuit is such that normally triode 18 is conducting and triode 19 is blocked because almost the whole positive voltage of source +B is impressed on the grid of triode 18 through resistor 84. The plate current of triode 18 flowing through the common resistor 8G results in a large eiective negative bias being applied to triode 19 in opposition to the positive bias applied by resistor 81 which continues to maintain triode 19 in a cut-off condition. When a negative pulse 88 of relatively short duration is impressed upon the grid of triode 18 this tube Will be driven towards cut-off With an attendant increase in the plate potential thereof. This increase in positive voltage will be impressed upon the grid of triode 19 through condenser 82 causing triode 19 to conduct plate current. The lresulting decrease in voltage at the plate of triode 19 further decreases the grid potential of triode 18 through the coupling condenser 83. This..

action progresses almost instantaneously until triodel` is driven 'beyond plate current cut-off 8 and triode 19 isconducting.` This condition con-nf tinues as long as the .charge of condenser 83 maintains the grid of triode 18 at a negative potential. When the condenser 83 has discharged through resistor 84 sufficiently to allow the grid of triode 18 to increase above the cut-oir value, triode 18 will again conduct current and the resultant action will reduce and eventually cut off the plate current of triode 19. This change-over action is relatively very rapid. The duration of the cycle of operation is dependent upon the time constant of the circuit including resistor 84 and condenser 83 and may be controlled as desired by proper selection of these elements. Triode 18 may also be returned to the conducting condition by a negative pulse 89 or 90 applied to the grid of triode 1S throughconductor 11 from the stop pulse input terminal 9|. The stop pulse would have to be very large if applied immediately after the application of the start pulse 88 to start pulse input terminal 92 in order to restore triode 18. to the conducting .condition but stop pulses of lesser and lesser amplitudes Would eiect the results as time goes on. A relatively small stop pulse would be effective just before condenser 83 becomes .discharged through resistor 84. The output voltage of the start-stop multivibrator of Fig. 7 is the Voltage of the anode of triode 18 as it appears at output terminal 93 which is con-v nected to the plate by conductor 94. The use of pulse control circuits of the kind illustrated in Fig. 6 with start-stop;multivibrators of the kind illustrated in Fig. ,'1 in an illustrative embodiment of applicants invention is shown in Fig. `8. The color cycle and synchronizingpulses after selection in synchronizing selector circuit'flS of Fig. 4 are impressed on amplifier 96 by conductor 95 and appear in conductor 52. In the integrating circuit 65 the color cycle pulses 31 are accentuated in amplitude relatively to the shorter duration eld scanning pulses 36A and in biasedf pulse inverter 89 selected and inverted Where they appear as negative pulses 88 in graph 9.1. Pulses 88 are impressed simultaneously by conductor 16 on the start pulse input terminals 92 of two startstop multivibrators 98 and 99 each of the kind shown in Fig.f7. The color cycle and synchronizing pulses in the output circuit of amplier 96 are impressed on pulse inverter 12 by conductors 52 and 11. Theyy appear as negative pulses 89 and 9B in the output circuit of pulse inverter 12 and v are impressed simultaneously on the stop pulse input terminals 9i of start-stop multivibrators 98 and 99.

The adjustment and operation of multivibrators 98 and 99 will now be described. As mentioned hereinbeore these multivibrators are each of the kind described with reference to Fig. '7. Multivibrator 98 which corresponds to the No. l multivibrator of Fig. 5 is adjusted so that the time constant of resistor 84 and condenser 83 will make triode 18 conducting again in the absence of a stop pulse in slightly more than one-thirtieth of a second after it has been made non-conducting by a start pulse. A relatively small stop pulse occurring one-thirtieth second after a start pulse 88, will stop the multivibrator and make triode 18 conducting one-thirtieth second after it was blocked by start pulse 88. A similar stop pulse '90 occurring one-sixtieth secondpafter va start pulse 88 will not be effective to make triode 18 conducting. vThis relationship is illustratedby Fig. 10 (H). Dotted line graph |60 shows the minimum amplitude of a stop pulse necessary to g make triode 18 againconducting afterit has been n blocked by a start pulse corresponding to a color cycle synchronizing pulse 31 indicated by points l| on graph |99. The stop pulse 90 corresponding to the rst leld synchronizing pulse 35 occurring one-sixtieth second after the vstart pulse 31 is not large enough to make triode 78 conducting but the stop pulse 99 corresponding to the second iield synchronizing pulse 36 occurring onethirtieth second after the start pulse 31 is large enough and does make triode 18 conducting. Therefore, the output voltage of the No. 1 multivibrator 98 is of the form shown by graph 60 in Fig. 10 (C). The amplitudes of the start pulses 88 are such that multivibrators 98 and 99 are started thereby in spite of the fact that stop pulses 89 are impressed simultaneously on stop pulse input terminals 9|. Y

Multvibrator 99 which corresponds to No. 2 multivibrator of Fig. is similar to multivibrator 98 but it is so adjusted that a rst stop pulse 90 occurring after a start pulse 88 will cause triode 18 to again become conducting. The time constant of the circuit including resistor 84 and condenser 83 of multivibrator 99 is adjusted so as to make triode 18 conducting again in the absence of a stop pulse in slightly more than onesiXtieth second after it has been made non-conducting by a start pulse. This relationship is illustrated by Fig. (J). Dotted line graph |82 shows the minimum amplitude of a stop pulse necessary to make triode 18 again conducting after it has been blocked by color cycle synchronizing pulse 31 indicated by the points |93 on graph |62. The stop pulse 98 `corresponding to the first field synchronizing pulse 36 occurring one-sixtieth second after the start pulse 31 will make triode 18 conducting. The second eld synchronizing pulse 36 occurring one-thirtieth second after the start pulse 31 will have no eiect because triode 18 of multivibrator 99 has been rendered conducting already. Therefore the output voltage of the No. 2 multivibrator 99 is of the form shown by graph 6| of Fig. 10 (D).

The output voltages of multivibrators 98 and 99 are used to control triodes 56 and 51 and their interconnections in the manner described vin connection with Fig. 5 to produce a color controlling voltage of the form shown in Fig. 10 (E). This voltage is used in the production of a television image in color as described hereinbefore with reference to Fig. 4.

An illustrative circuit which might be used for the color cycle synchronizing circuit 48 of Fig. 4 is shown in detail in Fig. 9. The synchronizing signals including the line scanning synchronizing pulses 35, the ordinary field scanning 'synchronizing pulses 36 and the color cycle synchronizing pulses 3'! as shown in Fig. 10 (B) are selected by the synchronizing selector circuit 45 and amplified by synchronizing pulse amplifier H8 forming `a part of the synchronizing selector circuit 45.

This amplier IIB comprises a triode a cathode-resistor H2, a coupling resistor II3, a

coupling condenser H4 and a load resistor H5. The integrating circuit 66 is the same as that described with reference to Fig. 6 which comprises a series resistor 6i and a shunt condenser 68. The voltage across condenser 69 is impressed on the input circuit of biased amplifier |16 comprising the triode 69, cathode biasing voltage divider l|1 consisting of cathode resistor |18, and

Vresistor H9, anda coupling resistor |29. lPulse inverter 12 consists rof a triode |2| a cathode resistor |22 anda coupling resistor |23. The grid of triode |2| has impressed thereon by vconductor 11 the synchronizing pulses carried by 'conductor 52. The starting pulses 88 corresponding to the color cycle synchronizing pulses 31 are impressed by conductor 24 on the start terminal |25 of the No. 1 Amultivibrator 98 through coupling condenser |26 and series resistor |21. Multivibrator 98 comprises two triodes |23 and |29, anode resistors |38 and |3|, switching condensers |32 and |33, grid biasing resistors |39 and |35, cathode resistor |36 and grid resistor |31. The resistance of resistor 34 and capacity of condenser |33 is so chosen that the normal period of the blocking of triode |28 after each starting pulse is slightly longer than one-thirtieth second as illustrated byFig. 10 (H). The stop pulses 98 corresponding to the field scanning synchronizing pulses'33 are impressed by conductor |38 on the stop pulse terminal |39 through coupling -condenser |40 andperies resistor |4|. The starting pulses 88 carried by conductor E24 are impressed simultaneously on the start terminal |45 of No. 2 multivibrator 99 through coupling condenser |46 and series :resistor |41. Multivibrator 99 comprises two triodes |48 and |49, anode resistors |58 and |5|, switching condensers |52 and |53, grid biasing resistors |54 and |55, cathode resistor |56 and grid resistor |51. The resistance of resistor |54 and the capacity of condenser |53 are so chosen that the normal period of the blocking of triode |48 after eachstarting pulse is slightly longer than one-sixtieth second as illustrated by Fig. 10 (J). The stop pulses 98 corresponding to the iield scanning synchronizing pulses 36 carried by conductor |38 are simultaneously impressed on the stop pulse terminal V|59 through coupling condenser |69 and series resistor 6|. The anode potentials for the triodes are furnished by direct current source +B. Cathode biasing voltages for triodes 69, |28, |29, |48 and |49 are obtained from the same source. The output voltages from multivibrators 98 and 99 arecombined in the vcircuit comprising triodes 56 and 51 and resistors-62 and 63 as described in connection with Figs. 5 and 8. The cathode biasing voltage for triode 55. is obtained from Voltage divider |62 consisting of resistors |63 and |64 connected in series across source -|-'B. The cathode biasing voltage for triode 51 is obtained from voltage divider |65 consisting of resistors |66 and |61 connected in series across the source +B.

In a modication of the circuit of Figs. 8 and 9 the pulse inverter 12 is omitted. The conductor 14 in Fig. -8 is connected to conductor 95. Amplifier 96 is then constructed to function asa pulse inverter. In Fig. 9 conductor |38 is connected to conductor 95. In both of these modications the pulses impressed on amplifiers 96 and ||0 are of negative polarity.

In place of the triodes of Fig. 9 and others of the gures, other suitable tubes may be used such as pentodes. Embodiments of the invention other than those described as illustrative hereinbefore will occur to persons skilled in this art. Such modications come within the pur view of the rappended claims. l

What is claimed is:

1. A system for Aproducing television images in color, comprising an limage-producing device having voltage control means for determining the color of ,the produced image, a source of video signals producing cyclically video signals corresponding to `the primary colors used to produce the images in color, a source of color cycle synchronizing signals `producing one current pulse only for each group of colors in a color cycle, means to impress video signals from said source on said image-producing device in color cycles of the primary colors, and means triggered by the current pulses of the color cycle synchronizing signals from said source to produce and impress color control voltages on said voltage control means to determine the color of the produced image.

2. A system for producing television images in colorcomprising a cathode ray tube having a luminescent screen adapted to produce light of different primary colors dependent upon the velocity of the bombarding electrons, means controlled by line and eld scanning pulses to eiTect eld scannings of said screen in succession, and means controlled by characteristic color cycle synchronizing scanning pulses consisting of one current pulse for each group of colors in a color cycle to control the velocity of the luminescent screen bombarding electrons to produce a color sequence of the primary colors.

circuit which separates the video signals from the synchronizing signals, a cathode ray tube including a source of electrons, a beam intensity control electrode, electron beam forming electrodes, horizontal deiiecting plates, vertical deilecting plates, a multilayer luminescent viewing screen adapted to produce light of the primary colors used in producing images in color dependent upon the velocity of the electrons in the beam as they strike the screen, and a multipleapertured electron velocity controlling electrode parallel and close to said multilayer screen, means to impress video signals from said synchronizing selector circuit on said beam intensity control electrode` means including said electron beam forming electrodes forming the electrons from said source of electrons into a beam, means utilizing said line scanning synchronizing pulses, said neld scanning synchronizing pulses, and said color cycle synchronizing pulses to produce line scanning voltages and eld scanning voltages and impressing said voltages on said horizontal deiiecting plates and said vertical deiiecting plates respectively, and a color cycle synchroniz- .ing means utilizing said color synchronizing pulses to produce velocity controlling voltages and impressing said voltages on said electron velocity controlling electrodes to determine the primary color produced during the successive iield scannings of said viewing screen.

4. A receiver for producing television images in color according to claim 3 in which the color cycle synchronizing means comprises a duration selection circuit including a series resistor, a shunt condenser and a biased triode having line scanning synchronizing pulses, field scanning synchronizing pulses and color cycle synchronizing pulses impressed thereon and producing only color cycle synchronizing pulses of opposite polarity than the impressed color cycle synchronizing pulses, a rst multivibrator controlled by said color cycle synchronizing pulses of opposite polarity and producing substantially square-topped pulses of the duration of two successive eld scannings, a second multivibrator also controlled by said color cycle synchronizing pulses of opposite polarity and producing substantially squaretopped pulses of the duration of one eld scanning, a iirst and a second triode each negatively biased to cut-off, a source of plate current for said triodes connected through a resistor to said rst triode and directly to said second triode, means to impress the square-topped pulses from said first multivibrator on the input circuit of said rst triode to cause plate current to iiow in said rst triode, means to impress the square-topped pulses from said second multi-vibrator on the input circuit of said second triode to cause plate current to flow in said second triode, and means to impress the plate voltage of said second triode on said electron velocity controlling electrode of said cathode ray tube.

5. A receiver for producing television images in color according to claim 3 in which the color cycle synchronizing means comprises a duration selection circuit including a series resistor, a shunt condenser and a biased triode having line scanning synchronizing pulses, iield scanning synchronizing pulses and color cycle synchronizing pulses impressed thereon andproducing only color cycle synchronizing pulses of negative polarity, a rst multivibrator having a start terminal, a stop terminal and an output terminal which is positive during the interval between the application of a start pulse and a stop pulse, a second multivibrator having a start terminal, a stop terminal and an output terminal which is positive during the interval between the application of a start pulse and a stop pulse, means to impress said color cycle synchronizing pulses of negative polarity on the start terminals of both said multivibrators, means to impress both eld scanning synchronizing pulses and color cycle synchronizing pulses of lesser amplitude on the stop terminals of both said multivibrators, said rst multivibrator being so adjusted that the color cycle synchronizing pulses impressed on the start terminal will be effective to produce a positive voltage pulse at the output terminal which is -terminated by the second field scanning synchronizing pulsel occurring after each start pulse and said second multivibrator being so adjusted that the color cycle synchronizing pulses impressed on the start terminal will be effective to produce a positive voltage pulse at the output terminal which is terminated by the rst field scanning synchronizing pulse occurring after each start pulse, a iirst and a second triode each negatively biased to cut-01T, a source of plate current for said triodes connected through a first and a second resistor in series to said first triode and through said second resistor only to said second triode, means to impress the square-topped pulses from said rst multivibrator on the input circuit of said first triode to cause plate current to flow in said iirst triode, means to impress the squaretopped pulses from said second multivibrator on the input circuit of said second triode to cause plate current to flow in said second triode, and means to impress the plate voltage of said second triode on said electron velocity controlling electrode of said cathode ray tube to determine the primary color produced during the successive iield scannings of said viewing screen.

6. A receiver for producing television images in color comprising a conductor of composite signals including video'signals:representative of the intensity characteristicsof-successive eldscannings of a field of view an image of which is to fbe produced in color, the `scannings of groups of successive field vseannings corresponding respec-` tively Ato the color components representative of vthe primary colors usediin .producing theimages incolor, .line scanning synchronizing pulses, eld scanning synchronizing pulses, rand color Vcycle synchronizing pulses, .a synchronizing selector: circuit vWhich vseparates vvthe Vvideo signals -from the synchronizingsignals, a-,cathode ray tube including a rsourceof electrons, fa beam intensity control electrode, velectron beam formi-ng elecjtrodes, horizontal Vdeflecting .plates, vertical de-i jlecting plates, `a .multilayer luminescent .viewing chronizing pulses to produce line scanning voltages and eld scanning voltages and impressing said voltages on said horizontal deflecting plates and said vertical deflecting plates respectively, and a color cycle synchronizing means utilizing said color synchronizing pulses to produce velocity controlling voltages and impressing said voltages on said electron velocity controlling electrode to determine the primary color produced during the successive eld scannings of said viewing screen, said color cycle synchronizing means comprising a duration selection circuit including a series resistor, a shunt condenser and a biased triode having line scanning synchronizing pulses,

field scanning synchronizing pulses and color cycle synchronizing pulses impressed thereon and producing only color cycle synchronizing pulses of opposite polarity than the impressed color cycle synchronizing pulses, a rst multivibrator controlled by said color cycle synchronizing pulses of opposite polarity and producing substantially square-topped pulses of the duration of two successive field scannings, a second multivibrator also controlled by said color cycle synchronizing pulses of opposite polarity and producing substantially square-topped pulses of the duration of one eld scanning, a rst and a second triode each negatively biased to cut-off, a source of plate current for said triodes connected through a resistor to said rst triode and directly to said second triode, means to impress the square-topped pulses from said rst multivibrator on the input circuit of said iirst triode to cause plate current to flow in said first triode, means to impress the square-topped pulses from said second multivibrator on the input circuit of said second triode to cause plate current to flow in said second triode, and means to impress the plate voltage of said second triode on said electron velocity controlling electrode of said cathode ray tube.

7. A receiver for producing television images in color comprising a conductor of composite signals including video signals representative of the intensity characteristics of successive field scannings of a field of view an image of which l is lto be `produced in ../color, the Jscannings :of

ffgroupsfof successive iield fscannings corresponding Vrespectively `to 4the color Acomponents representative :of the primary colors used in producing the images in color, line scanning synchronizing pulses, field scanning synchronizing pulses, and color cycle-synchronizing pulses, a

electron beam forming electrodes, horizontal deilecting plates, vertical ',deflecting plates, a multilayer luminescent viewing screenzadapted to yproduce light of the primary colors used in producing images incolor dependent upon the velocity of the electrons in the beam as they strike the screen, and an electron velocity controlling electrode parallel and close to said multilayer screen, means to impress video signals from said synchronizing selector circuit on said beam intensity control electrode, means including said electron beam forming electrodes forming the electrons from said source of electrons into a beam, means utilizing said line scanning synchronizing pulses, said eld scanning synchronizing pulses, and said color cycle synchronizing pulses to produce line scanning voltages and eld scanning voltages and impressing said voltages on said horizontal deilecting plates and said vertical deecting plates respectively, and a color cycle synchronizing means utilizing said color synchronizing pulses to produce velocity controlling voltages and impressing said voltages on said electron velocity controlling electrode to determine the primary color produced during the successive field scannings of said viewing screen, said color cycle synchronizing means comprising a duration selection circuit including a series resistor, a shunt condenser and a biased triode having line scanning synchronizing pulses, field scanning synchronizing pulses and color cycle synchronizing pulses impressed thereon and producing only color cycle synchronizing pulses of negative polarity, a rst multivibrator having a start terminal, a stop terminal and an output terminal which is positive during the interval between the application of a start pulse and a stop pulse, a second multivibrator having a start terminal, a stop terminal and an output terminal which is positive during the interval between the application of a start pulse and a stop pulse, means to impress said color cycle synchronizing pulses of negative polarityl on the start terminals of both said multivibrators, means to impress both eld scanning synchronizing pulses and color cycle synchronizing pulses of lesser amplitude on the stop terminals of both said multivibrators, said first multivibrator being so adjusted that the color cycle synchronizing pulses impressed on the start terminal will be eiective to produce a positive voltage pulse at the output terminal which is terminated by the second field scanning synchronizing pulse occurring after each start pulse and said second multivibrator being so adjusted that the color cycle synchronizing pulses impressed on the start terminal Will be effective to produce a positive voltage pulse at the output terminal which is terminated by the first eld scanning synchronizing pulse occurring after each start pulse, a first and a second triode each negatively biased to cut-01T, a source of plate current for said triodes connected through a first and a second resistor in series to said rst triode and .2,580,078 15 16 through said second resistor only to said second REFERENCES CITED triode, means to impress the square-topped The followin reference are of r or pulses from said rst multivibrator on the input fue of this paint: s ec d m the circuit of said rst triode to cause plate current to ow in said rst triode, means to impress the 5 UNITED STATES PATENTS square-topped pulses from said second multi- Number Name Date vibrator on the input circuit of said second 2,096,986 Von Ardenne Oct. 26, 1937 triode to cause plate current; to flow in said sec- 2,309,506 Herbst Jan. 26, 1943 ond triode, and means to impress the plate volt- 2,343,825 Wilson Mar. 7, 1944 age of said second triode on said electron ve- 10 2,378,746 Beers June 19, 1945 locity controlling electrode of said cathode ray 2,431,088 Szegho Nov. 11, 1947 tube to determine the primary color produced 2,440,301 Sharpe Apr. 27, 1948 during the successive field scannings of said 2,446,248 Shrader Aug. 3, 1948 A viewing screen. 2,446,764 Henderson Aug. 10, 1948 15 2,452,522 Leverenz Oct. 26, 1948 JOSEPH A. BURTON. 2,455,710 Szegho Dec. 7, 1948 

